Classifier deck



March 8 1927. 1,620,243

' A. H. SjrE'BlNS cLAssLF/IER DEx Filed Jan -2o. 1325. s sheets-Sheet 1" d fr,

/N VEA/TOF? A TfrdR/VEY March s, 1927.-

A, H. sTEBBlNs' CLASSIFI'EH DECK Filed Jan. 2 0, 1926 v 5 Sheets-Shea?I 2 ATTORNEY March 8 1927 Filed Jan. 20. 1925 A. H. STEBBINS CLASSIFIER DECK' 3 Sheets-Sheet 3 J1 sa lll A T/EN To@ d/M%M ATTO RNY Patented Mar. 8, 1927.

' UNITED STATES APATErrr OFFICE.

ALBERT I-I. STEBBINS, OF LOS ANGELES, CALIFORNIA.

CLASSIFIEB DECK.

Application filed January 20, 1926. Serial No. 82,408.

This invention relates to a novel deck construction which is adapted prlmarlly to classify materials, but which serves also to some degree as a concentrator deck.

Air concentrator tables as constructed heretoforeare commonly provided with a deck having' a laterally inclined deck surface in which apertures are formed thruout practicallyv the entire surface of the deck, riftles are pro-vided over the deck surfaceto direct the concentrates or values lengthwise of the deck while the lighter materials or .tailings are caused to flow laterally over the sideof the deck, and movement is commonly imparted to the deck to advance the materials along its surface.

In operating these concentrator tables. of Well'known construction, in orderv to secure good results it is necessary to carefully con* trol the strength of the air thruout the deck surface, which requires very careful adjustment of the aperture openings. It is also necessary to carefully regulate the strength and nature of the movement imparted to the deck, and to regulate the feed of the materials and other operating conditions.

The present invention contemplates certain 'changes in the construction and operation of concentrator decks whereby the materials being treated will be rapidly classilied in an `extremely satisfactory manner; that is, instead of operating ythe deck to concentrate materials as heretofore, it is operated to classify the materials. In this manner the classification of materials, which has been effected heretofore'in variously constructed air chambers, can be effected in an extremely satisfactory manner upon what may be termed a classifier deck.

The term classification is herein used to designate the separation of different materials into different con'ipartments in accoi-dance with their size and weight, so that materials having a particular size Vand weight are deposited in one compartment while materials of a slightly different size and weight are placed in the next compartment. In the present case the compartments in which the different size materials are placed are formed by the ril'l'les that divide the deck surface into successive compartments.

In order to make clear the construction and operation of the presen-t classifier deck as distinguished from the concentrator decks as usually constructed heretofore, it is .thought advisable to first consider the important feature of the usual concentrator deck.

In the ordinary concentrator deck the strength of the air passing up thru the apertures,` formed tln'uoutl the deck such that the air will lift the small light particles and carry ofl:i the dust, but it is not strong enough to disturb the st-ratifying operation that is taking place over the deck surface under the action ofthe deck move" ment. The deck surface is usually inclined transversely so that the lightermaterials that are crowded upwardly away from the deck surface by the heavier materials will flow laterally over the riilles, while the heavier materials travel along the riflies toward the concentrate wall.`

In accordance with the present invention the deck is constructed and operated so that its primary object is to separate out and promptly dispose of t-he lighter materials or tailings at the lower side of the deck, and, altho the values or concentrates that remain on the deck surface may be subjected to a concentrating operation, this is of secondary consideration. As a matter of fact two separate and distinct separating' operations are carried out upon the deck in ac cordance with the present invention; that is, in the vicinity of the apertures the air produces a classification both as to size and as to gravity, while as t-he materials advance further along the deck they undergo a movement separation or classification.

One important feature of the present invention resides in a deck surface having apertures formed in only that part of the surface which lies near the material receiving end of the deck, and in the action of the air whereby a classification of the lighter materials or tailings is effected.

Another important feature of therinvention vresides in a deck having a relatively wide band-like portion extending across the deck surface and forming an inclined or up-hill section up which the materials must travel in moving lengthwise of the deck. This construction retards the movement of the tailings lengthwise ofthe deck and helps to separate them from the concentrates traveling along the deck.

This api-hill feature has a further ad.

vantage in that it serves to remove most of the fine light particles before the concentrates reach the crest of the hill, and as surface is l a result it is feasible to impart a. downhill slope to the remaining portion of the deck; this permits the angle of the riifles relative to the lower side of the deck to be-increased, which is desirable as it increases the number of riiles terminating along the concentrate wall.

Still another feature of the invention resides in the construction of the cover eX- tending over the apertured portion of the deck surface whereby the air which is removed from the chamber below this cover is caused to flow transversely of the deck surface to thereby promote movement of the lighter materials toward the lower side of the deck.

Other features of the invention and novel combination of parts in addition to the above will be hereinafter described in connection with the accompanying drawings which illustrate good practical forms of the invention.

In the drawings Fig. 1 is a` top plan view of ak deck constructed in accordance with the present inventi-on;

Fig. 2 is a side view of the deck of Fig. 1,'and of the deck supporting frame;

Fig. 3 is a sectional perspectiveview of the deck of Fig. 1, but shows the apertures as extending only part way across the deck surface;

Fig. 4 on an enlarged scale is a sectional view taken on the line 4.-1 of Fig. 1 and shows the elimination of the values from the tailings as the latter move transversely down the deck surface;

Fig. 5 is a diagrammatic view showing the approximate disposition of the different materials upon the deck surface.

Fig. 6 is a plan view of a modified type of deck;

Fig. 7 is an enlarged sectional view taken on the line 7-7 of Fig. 6;

Fig. 8 is a side view of the deck of Fig. 6;

-Fig 9 is a sectional view taken on the line 9 9 of Fig. 1;

Fig. 10 is a sectional view taken on the line 10-10 of Fig. 1; and

Fig. 11 is a perspective view of a wing to be described.

The configuration of the deck casing forming the subject Vmatter of the present invent-imi may be varied as desired, and the deck shown is elongated in sha-pe and is relatively wide at its material receiving end and tapers to a much narrower width towards its discharge end. The deck casing may be variously constructed and is provided with an air chamber 10 disposed below the deck surface 11 and the materials to be treated "are delivered to the deck surface by a hopper 12 mounted at the upper side of the deck and adjacent the left-hand end thereof, viewing Fig. 1. The deck surface 11 is preferably supported so that it slopes in a transverse direction towards the lower or discharge side of the deck, and is provided with a concentrate wall 13 that extends along the upper side of the deck.

The frame for supporting the deck so that it may partake of a back and forth or vibratory movement that will advance the materials over the deck surface may be variously constructed, and the supporting frame, as shown in Fig. 2, is provided with the uprights 11i to which the longitudinally extending rails 15 are secured. The means for mounting the deck upon its frame so that the deck may partake of its vibratory movement may be varied as desired, and in the construction shown the deck is mounted upon a supporting carriage 16 and is preferably secured thereto atits lower side by the hinges 17; this construction is desirable because it permits the transverse inclination of the deck to be varied as desired. In the construction shown the supporting frame is provided near its opposite ends with the transversely extending shafts 18 having the downwardly extending arms 19. These arms are provided with laterally extending stub shafts 2O which are journaled in bearing blocks 21 secured to the under face of the carriage 16, the arrangement being such that as the deck moves back and forth in the direction of its length, it will rise and fall slightly in a. well known manner.

Various means might be provided for imparting a back and forth movement to the deck, and the means shown to this end consists of a power operated shaft 22 which is rotatably supported by the machine frame and is provided with an eccentric 23 upon which is mounted the grooved sheave 24. About this sheave is passed a cable 25 one end of which is secured to the carriage frame 16 and the other end is fastened to the machine supporting frame by a bolt 26 provided with adjusting nuts 27. The operating shaft and eccentric just described will serve to move the sheave 241 bodily towards and from the cable tightening position and this will serve to pull the deck in a left-hand direction viewing Fig. 2. The means shown for urging the deck in the opposite direction consists of a cable 28 having one end anchored to the carriage 16, and the opposite end secured to a. spring 29. while an intel'- mediatc portion of this cable passes about an idle sheave 30. rl`he means just described will serve to move the dcck back and forth, and in order that the movement of the deck in a right-hand direction may be suddenly checked to advance the materials lengthl wise of the deck, an abutment 3l of any desired construction may be provided, which is secured to the machine frame and is positioned to be engaged by an adjustable bolt or the like 32 carried by the carriage 16.

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As above indicated, one V,of the features of the present invention resides in a deck the deck surface of which has apertures formed only in that portion of its surface which lies near the materialrece'iving end of the deck. The size and shape of the area of the deck surface which is provided with the apertures 33 may be varied as desired, and is shown as having the form of a relatively wide band extending diagonally across the deck from the hopper' 12 towards the lower discharge side of the deck. In Fig. 1 these apertures are shown as extending entirely across the deck, whereas in Fig. 3 they are shown as terminating some distance from the lower side of the deck, as indicated by 34. Since only the portion of the deck surface 11 lying near the material receiving. end of the deck is provided with apertures, the air chamber need extend under only that portion of the deck surface which is provided with apertures. The air chamber below the deck surface is therefore provided with a partition or wall extending transversely of the deck surface in an inclined direction, and since a small amount of fine material may pass downwardly thru the apertures 33 into the chamber 10 it is desirable to provide means for removing this fine dust-like mate* rial, and the partition 35 is therefore shown as having a. portion thereof cut away as at 36 to form an opening thru which the materials may escape from the chamber 10 under t-he action of the progressive movement imparted to the deck.l Such air as may escape fromv the chamber 10 thru the opening 36 will be confined in a smaller chamber 37 formed und-er the deck surface and having the confining walls 38 and 39, and the air may be exhausted from the chamber 37 by a pipe or the like leading from this chamber to suitable exhaust means. The wall 39 may be provided with a small opening 40 through which the materials resting upon the lower floor 41 of the deck may pass towards the discharge spout or opening 42 with which the floor 41 is provide It is desirable to form a casing over the apertured portion of the deck surface in order to confine the air and dust rising from the deck surface. The means shown to this end consists of a cover plate 43 which is supported in spaced relation to the deck surface and the air which is confined in the space below the cover 43 may pass upwardly to a hood 44 which communicates with the chamber just mentioned thru the relatively large opening 45 formed in the cover plate 43. The hood 44 may be connected to any suitable exhaust means not shown for carrying off the air and dust above the deck surface. It should be noted that the opening 45 is disposed at the lower or material discharge side of the deck. This position of the opening is highly desirable because it causes the air in the chamber below the cover 43 to travel transversely of the deck surface in passing towards the exhaust means. This traverse movement of the air helps to carry the lighter particles transversely of the deck towards the discharge side thereof, which is very desirable.

Since the apertures 33 are formed in only a portion of the deck surface, the deck cover 43 extends over only a portion of the deck and a resultl air may tend to enter 'the air chamber below the cover 43 along the edge 46 of this cover, that is, between the edge 46 and the deck surface. To prevent this the apron 47 is provided, which is secured to the i under face of the cover 43 adjacent its edge 46 and this apron` extends downwardly as close to the deck surface as is practical. As a result of this construction such air as may enter between the lower edge of the apron 47 and the deck surface will serve to carry back into the chamber such dust as might tend to escape below the apron 47. A

The air passing upwardly thru the aperture-s formed near the hopper 12 may tend to travel lengthwise of the concentrate wall 13 and escape from under the cover 43 along this wall. To prevent this the wings 48 may be provided which are conveniently secured to the buffe-r blocks 49, as best shown in Fig. 11 and these wings are given suilicient width to extend from the under face of the cover plate 42 downward nearly to the deck surface. The ends of the wings 48 may be curved as at 50 so that they will. direct back under the cover the air that might otherwise escape along the concentrate wall, and these wings have a laterally extending flange portion 51 adapted to catch the lighter particles adjacent the wings and to direct these part-icles back under the cover.

The heavier materials or concentrates are directed against the concentrate walls by riffles 52 which are shown in Fig. 6 as extending diagonally over the entire deck surface. These riiiies it should be noted are shown in Figs. l and 3 as extending diagonally over only the portion of the deck surface which is uncovered, and the riflles 53 lying under the covered portion of the deck surface are shown as extending substantially parallel to the lower side of the deck. This construction is desirable because ofl the peculiar construction of that portion of the deck surface lying under the cover plate 43 and which will now be described.

As above pointed out one of the important features of the present invention resides in the construction whereby a portion of the deck surface disposed near the material rei ceiving end of the deck is given an up-hill slope, as indicated by 54 whereby the mate` rials traveling lengthwise of the deck are caused to move up this inclined'surface. As

al result of this construction the materials resting' upon the deck surface under the cover t3 are subjected not only tothe transverse inclination of the deck surface, but also to the up-hill slope 54E which retards the travel oit' the lighter materials lengthwise et the deck, thus materially increasing;i the tendency oit' the lighter materials te separate out frein the heavier materials er concentrates before the latter pars over `he crest of the hill indicated by As a result of the construction liust described, whereby most of the lighter nuiterials and tailings are removed from the concentrates before the latter pass over the crest of the hill, the remaining portion of the deck surface G may be `given a. downward inclination, as best shown in Fig'. rlhis will help to advance the materials lengthwise of the deck and permits the use of rii'tles which may extend diagonally of the deck surface at an increased angle relative to the lower side of the deck; this arrangement seing` desiralfle as it increases the number of ri'tlies terminating alongthe concentrate wall 13. ln the operation of the deck forming` the. subyect matter of the present invention it is desirable that the air currents pesi-ling` upwardly thru the apertures 33 shall be strongest at the upper side of the deck and that these currents shall gradually decrease in strength as the materials pass downwardly towards the lower side ofthe deck. This variation in the strength of the air currents is readily obtained by varying the size of the opening of the apertures 33, as clearly shown in Fig, 't'. wherein it will be noted that. the lips 57 of the apertures near the upper side of the deck are bent upwardly to form openings which are much larger than the opening; of the apertures near the lower side of the deck. As a result of this construction the strong,l currents of air passing,` upwardly thru the materials upon the deck surface near the hopper 12 will quickly lift the lighter matcrials and tailings so that the heavier particles or concentrates may work downwardly close to the deck surface and these strong' air currents will promote a rapid flow ot' the lighter materials transversely of the deck towards the lower side thereof. The large heavy concentrates will of course settle between the riilles near the upper side of the deck and will quickly reach the concentrate wall. while the somewhat smaller concern trates will settle between the rililes di p further .flown the deck and the lichter particles and tailings will arrange thenselvrs between the riftles lying; still further down the laterally inclined deck, thus producing the classifying effect above mentioned. The rip-hill portion 5l as previously stated will retard the movement of the lighter materi als and tailings lengthwise of the deck and a result there lighter particles continue to flow transversely along the deck surface Aover the various ritlles andare discharged at the lower side of the deck. The manner in which the concentrates gradually separate out from the tailings as the latter move downward across the inclined deck is clearly indicated in Fig. e whereinthe concentrates are designated by C and the tailings are designated by T.

Due to the up-hill slope given to the portion 54 of the deck it is not feasible to place the riliies extendingr over this portion of the deck at a transverse inclination to the direction of movement. They are therefore shown as extending' substantially parallel to the lower side of the deck, so that they will not unduly retard the movement of the heavier materials lengthwise ot' the deck. The transverse movement of the air above mentioned may cause some of the liner particles to drop upon .the unperforated portion 5S of the deck, in which case the materials will merely travel along the ritlles under the action of the deck movement until they reach the apertured portion of the deck. lf desired the portion of the deck indicated by 58 may be given al down-hill slope, as shown in the modification of Fig. 8 since this inclination will help advance the materials lengthwise of the deck.

Air under pressure may be supplied to the air chamber below the deck surface by the pipe or conduit 59, and in the construction shown in Figs. 1, 2 and 3 employing a deck surface having` the up-hill portion 54, the apertures 33 are preferably omitted at the crest of the hill, as the omission of these apertures will tend to slow down the movement of the concentrates lengthwise of the deck. This slowing down of the movement of the concentrates will tend to prevent the tailings from traveling lengthwise of the deck suiliciently to escape from under the cover 43.' Since air is eX- hausted by the means described from the chamber under the cover 43, air from the atmosphere may tend to enter this chamber along` the lower side of the deck where the tailings are discharged. In order to prevent air from entering the chamber at this point a canvas apron 60 may be provided the upper ed ge of which may be secured to the cover 43 so that this flexible apron will hang downwardly over the tailings discharge opening, and a bar 6l secured to the lower edge of this apron will serve as a weight to keep the apron tensioned, while. the same time it will permit the materials discharged from the lower side of the apron to fall between the' apron and the side of the deck.

Since in the present construction air is forced upwardly thru apertures formed only in a portion of the deck surface a smaller volume of air will suiice to operate the present deck than is required to operate the Cli Btl

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type of' decks employed heretofore lhaving apertures formed thruout the entire deck surface. This permits a saving in power in supplying air to the deck and also in eX- hausting it therefrom. Furthermore, since the cover 43 extends over only 'a portion of the deck the operation of the materials upon the uncovered portion may be readily observed, which is desirable.

The portion of the concentrate wall 13 lying under the cover 43 may be constructed so that it projects inwardly a substantial distance over the deck surface as at 62. This will produce an accumulation of concentrates against this part of the wall and will help to push the tailings down the inclined deck. y

The modified construction shown in Figs. 7 and 8 is substantially similar in construction and operation to the construction shown in Figs. l, 2 and 3 except that the deck in this modified construction is not provided 4with the hump or up-hill portion 54 of Figs. l, 2 and and as a result the finer materials and tailings will not separate out as quickly in the modified construction as they will in Figs. l, 2 and 3.

The condition of the materials being treated upon different portions of the deck shown in the various views of the drawings will be better understood upon reference to the diagrammatic view shown in Fig. 5, wherein dot-and-dash lines extending` over the deck surface are provided to outline the approximate areal in which the different separating operations occur. The section of the deck shown in Fig. 5 as designated by I is the portion of the deck upon which the small light particles are dropped by the air traveling transversely of the deck surface and which particles are returned to the apertured portion of the deck bv the deck movement. The section of the deck indicated by II is that portion in which the air classifying operation takes place and it is this portion of the deck which serves to rapidly separate out the tailings and also the very .fine values which it is not practical to treat upon the present machine without materiallv slowing down the classifying operation. The area designated by IH is that section in which a movement classification takes place; that is, the lighter materials which travel along the. rifiies into thisA area will reach the concentrates that are lying b-etween these rifiies as a result of the cross flow of the concentrates adjacent the concentrate wall. The. movement of these lighter' materials and tailings against the 'bank of heavier materials will force the lighter materials up over the top of the riffies to flow transversely of the deck towards the discharge side. The section ofthe deck designated by IV is thatA section in which the coarse and 'line concentrates collect, asit is the area lin which the concentrates `that are approaching the concentrate` wall meet the concentrates that have piled up against the concentrate wall and have fallen away from the same. The narrow section 5 designates the area in which the tailings are almost entirely removed from the concentrates.

As a result ofthe deck construction described it will be seen that all waste or light gravity materials under a certain determined size are quickly disposed of by the action of the air which effects their travel across the deck toward the discharge side thereof. At the same time all values or heavy gravity particles of al much smaller size are likewise quickly disposed of at the lower side of the deck. The material remaining on the deck consists of relatively coarse waste and all Values except the extremely fine. values. These remaining materials may be readily separated by movement alone, thus avoiding the use of air apertures throughout a. large portion of the deck.

What is claimed is:

l. A deck for separating materials, comprising in combination, a deck casing that is supported at a transverse inclination' and has a. feed hopper at the juncture of the upper side and one end of the deck, a deck surface which is provided with apertures in only that portion of the deck disposed near the feed hopper, said apertures being largest in the vicinity of the feed hopper and decreasing in size downwardly across the deck, riiiies extending over the deck surface, means' for forcing` air upwardly through the apertures to effect a classification of the materials in the vicinity of the feed hopper, and means for vibrating the deck to advance the materials over the deck surface and to effect a movement stratification of the materials as they ltravel over the unapertured portion of the deck surface.

2. A deck for separating materials, comprising in combination, a deck casing having a feed hopper at one end, a deck surface that is supported at a transverse inclination and which is adapted to effect a classification of the materials near the hopper,` and a concentration of the materials throughout the remaining port-ion of the deck, said surface being provided with apertures only in the portion of the deck near the hopper where the classication of the materials is effected and formed with a hump port-ion extending transversely of the deck near said hopper to form a hill up which the materials must trave-l as they move lengthwise of the deck from the classifying port-ion of the deck to the concentrating portion, rifiies 'extending over the deck surface, and means for operating the deck to advance the materials over its surface. p

3. A deck for separating materials, comprising in combination, a dec-k casing havllO Cil

ing a deck surface that is provided with a hump portion extending transversely of t-he deck to form a hill up which the materials must travel as they move lengthwise of the deck, riifles extending up the hill portion of the deck and other ritlies extending over a different portion of the deck surface and arrangedat an angle to the ritiles upon the hill portion, and means for operating the deck to advance the materials over the same.

et. A deck for separating materials, comprising in combination, a deck casing having adeck surface that is provided with a hump portion extending transversely of t-he deck to form a hill up which the materials travel as they move lengthwise of the deck, rililes extending up the hill portion of the deck and arranged substantially parallel to the tailing discharge side of t-he deck, other riliies extending diagonally over a. different portion of the deck surface at an angle to the first mentioned rifiies, and means for operating the deck to advance the materials over the same.

5. A deck for classifying materials, comprising in combination, a. deck casing provided with a laterally inclined deck surface having apertures formed only in that part of the deck surface that is disposed near the material receiving end of the deck and having a large unapertured portion, means for forcing air thru the apertures with sutlicient pressure to promote a rapid movement of the lighter materials transversely of the deck toward its discharge side, and riflles for directing the heavier particles lengthwise of the deck and arranged to extend over both the apertured and unapertured portion ofthe deck.

6. A deck for separating materials, comprising in combination, a deck casing having a deck surface that is provided near the material receiving end of the deck with a wide portion that slopes upwardly to form a hill extending across the deck up which the materials travel as they move lengthwise of the deck and the portion of the deck surface extending from the crest of the hill toward the discharge end of the deck being constructed to slope downwardly to promote travel of the materials toward the discharge end of the deck, rifiles upon the deck surface, and means for operating the deck to advance the materials over its surface.

7. A deck for separating materials, comprising in combination, a deck casing having a deck surface that is provided near the material receiving end of the deck with a wide portion that slopes upwardly to form` a hill extending across the deck up which the materials travel as they move lengthwise of the deck and the portion of the deck surface extending from the crest of the hill toward the discharge end of the deck being constructed to slope downwardly to promote travel of the materials toward the discharge end of the deck, said deck surface having air apern tures formed only in the part of its surface that is disposed near the material receiving end of the deck, riiiles upon the deck surface, and means for operating the deck to advance the materials over its surface.

8. A deck for separating materials, comprising Vin combination, a deck casing having a deck surface that is provided near its material receiving end with a wide portion that slopes upwardly to form a hill extending across the deckup which the materials travel as they move lengthwise of the deck and the portion of the deck surface extending from the crest of the hill toward the discharge end of the deck being provided with diagonally disposed rifl'les and constructed to slope downwardly to promete travel of the n'iaterials along the inclined rifiles, and means for operating the deck to advance the materials over its surface.

9. A deck for separating materials, comprising in combination, a deck casing having a deck surface that is provided near its material receiving end with a wide portion that slopes upwardly to form a hill extendingacross the deck up which the materials travel as they move lengthwise of the deck, riiiles upon the deck surface, said up-hill portion of the deck surface being provided with apertures to promote separation of the tailings from the values before the latter' pass over the crest of the hill, a cover extending` over 'the aperturedportion of the deck to form a dust compartment, and means for operating the deck to advance the materials along the same.

' l0. A deck for separating materials, comprising in combination, a deck casing that is supported at a transverse inclination and has a feed hopper at one end, a deck surface which is provided with' apertures in 'only that portion of the deck disposed near the feed hopper and the apertures being leargest near the upper side'of the deck and gradually decreasing in size toward the lower side of the deck, a cover extending over the apertured portion of the deck surface to form a dust compartment, and means for exhausting air from the dust compartment at a point near the lower side of the deck to promote movement of the lighter materials with the air toward the lower side of the deck..

ll. A deck for separating materials, comprising in combination, a deck casing having an apertured deck surface, riftles upon the deck surface, a coverl extending over only the portion of the deck surface that is adj acent the material receiving end of the deck, means for exhausting air from the dust chamber under the cover, and an apron extending downwardly from the end portion of the cover into close proximity to the deck surface to prevent air from entering the an apertured deck surface,

dust chamber at points between the end of the cover and the deck surface.

12. A deck for separating materials, comprising in combination, a deck casing having an apertured deck surface, ritfles upon the deck surface, a concentrate wall extending along one side of the deck, a cover extending over only the portion of the decksurface that is adjacent the material receiving end of the deck and said apertures being formed only in that portion of the deck surface that lies below the cover, means for forcing air upwardly thru the apertures, and a wing disposed along the concentrate wall under the cover and constructed to direct back under the cover the air currents that tend to pass out from under the cover along the concentrate wall.

13. A deck for separating materials, comprising in combination, a deck casing having rililes upon the deck surface, a cover extending over the deck surface, a. concentrate wall extending along one side of the deck and having a portion near the material receiving end of the deck that projects inwardly a substantial distance over the deck surface to produce an accumulation of concentrates near said end of the deck, and means for actuating the deck to advance the materials over its surface.

lll. A deck for separating materials, coinprising in combination, a deck casing having an apertured deck surface but having the apertures omitted from a. portion of its surface lying at the discharge side of the deck near its material receiving end, a cover extending over the deck surface and provided with means for withdrawing air from the dust compartment below the cover at a point above said unapertured portion of the deck, and riflies upon the unapertured portion of the deck for direct-ing toward the apertures the materials that settle out of the air upon the unapertured section.

15. A deck for separat-ing materials, comprising in. combination, a. deck casing that has a feed hopper at one end, an apertured deck surface that is supported at a transverse inclination and which has an upwardly inclined portion extending across the deck surface near the feed hopper and up which the materials must travel as they move lengthwise of the deck, ritfles extending over the deck surface, a cover mounted over the deck surface to form a dust compartment, and means for exhausting air from the dust compartment at a point near the lower side of the deck to promote -movement of the lighter vceiving materials with they air toward the lower side of the deck.

1G. A deck for separating materials, comprising in combination, a deck casing having a transversely inclined deck surface, riftles extending over the deck surface, and the deck surface having an apertured section in the form of a wide band extending diagonally across the deck surface from the material reportion of the deck to the tailing discharge side of the deck and having the apertures omitted from the other portions of the deck surface.

17. A deck for separating materials, comprising in combination, a deck casing having a transversely inclined deck surface and having near the material receiving' end of the deck a wide hand-like portion of the surface that extends diagonall7 across the deck from the upper side of the deck to the tailing discharge side and disposed to form a hill up which the materials must travel as they move lengthwise of the deck, and riiiies extending over the hill portion of the deck surface and also over a large area of deck surface lyin between the said hill portion and thel delivery end of the deck.

18. A deck for separating materials, comprising in combination, a deck casing having a transversely inclined deck surface and having a wide band-like portion of the surface that extends diagonally across the deck from the material receiving portion thereof to the trailing discharge side of the deck and disposed to form a hill up which the materials must travel as they move lengthwise of the deck, said deck surface having apertures formed only in the vicinity of its wide handlike portion, and riffles extending over the deck surface.

19. A deck for separating materials, comprising in combination, a deck casing having a deck surface that is provided with an up wardly inclined portion forming a hill extending transversely of the deck and up which the materials travel as they move longitudinally of the deck, said deck having aper tures formed in the portion of the deck surface that constitutes the side of the hill but omitted from the crest of the hill to slow down the movement of the materials at the top of the hill, riltles upon the deck surface, and means for operating the deck to advance the materials over the same.

Intestimony whereof, I have signed my name to this speciiication.

ALBERT H. STEBBINS.

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